Blowby gas flows from the combustion chamber of an engine, through the gap between the piston and cylinder and into the crankcase. This blowby gas becomes a cause of air pollution, so it is necessary that the blowby gas be returned again to the combustion chamber and burned. Therefore, a breather apparatus is used, and by connecting the cylinder head with the air intake system by a breather pipe, this breather apparatus leads the blowby gas from the crankcase to the air intake system.
However, oil mist is included in the blowby gas inside the crankcase, so it is essential that the oil mist be separated from the blowby gas. Therefore, a breather apparatus having simple construction has been developed that separates the oil mist from the blowby gas by installing an oil separator on the cam shaft and turning the oil separator (for example, refer to Japanese Laid-open Patent Publication No. 2009-30580).
By using the breather apparatus disclosed in Japanese Laid-open Patent Publication No. 2009-30580, it was possible to remove a large amount of oil mist from the blowby gas, however, it was difficult to completely remove the oil mist from the blowby gas. The oil mist that is included in the blowby gas is a cause of soiling of the air cleaner element of the air intake system. Therefore, it is desirable that a large amount of the oil mist be removed, while at the same time maintaining the simple construction of the breather apparatus.